In the fabrication of integrated circuits, a number of the steps involved, for instance, in preparing integrated circuit chips and the packaging for the chips (articles to which the chips are attached and protected), are etching processes. Accordingly, over the years, a number of vastly different types of etching processes to remove material, sometimes in selective areas, have been developed and are utilized to varying degrees. One such etching process is referred to as "plasma etching". This type of etching procedure generally involves filling a container such as a bell jar with a gas whose dissociative fragments are chemically reactive. An example of such a gas is CF.sub.4. The surface that is to be etched is introduced into the container, along with the reactive gas. In the event the surface to be etched is to be etched only in certain predetermined areas, such surface would previously be covered by a mask to prevent etching in the areas not to be etched. The feed gas is usually dissociated, forming positive and negative ions, electrons, and reactive neutrals by coupling radio frequency power to the plasma by a capacitive or inductive coupling. It is believed that the reactive fragments then chemically interact with the surface to be etched. In such a process, the substrates may be positioned either on a ground plane on the rf driven electrode (cathode) or on an electrically insulated carrier.
Plasma etching has been used to a significant extend, depending upon the particular reactive gas employed for etching both organic and inorganic materials. Such materials include polyimides, polyepoxides, photoresists, and silicon.
For instance, polyimides are used to a large extent as insulation between two layers of metallization in multilevel metallization articles such as metallized ceramics. In such articles, two layers of metal, such as aluminum, an aluminum alloy, or copper are separated by a layer of insulating dielectric material such as a polyimide that contains vias in a predetermined pattern. The vias in the polyimide dielectric layers are formed by plasma etching. The gas employed, whose dissociative fragments are chemically reactive for etching polyimides include CF.sub.4 and oxygen, and mixtures thereof.